The yen is doing something it hasn't done since the 2010 'Flash Crash'

Investing.comThe yen is on fire after the Bank of Japan stunned the markets.

The Japanese yen is up by 3.1% at 107.98 a dollar as of 3:36 p.m. ET.

This is the biggest surge since the May 6, 2010 "Flash Crash," when the Dow plunged 998.5 points, according to Bloomberg.

The yen is now approaching its strongest level against the dollar since October 2014.

Earlier in the day, much to everyone's surprise, the BOJ held its asset-purchase program at an annual rate of about 80 trillion yen in an 8-to-1 vote. Economists were expecting the bank to increase the size of the program.

Additionally, the bank help its key interest rate at -0.10% and lowered its growth and inflation forecasts for the next coupe of years.

"The Bank of Japan's decision to forgo additional easing today came as a major disappointment to markets and resulted in a sharp appreciation of the yen," wrote Capital Economics' Marcel Thieliant. "Amid sluggish growth and moderating price pressures, we still think that more monetary stimulus will be announced before long, most likely in July but perhaps as soon as June."

As for the rest of the world, here's the scoreboard:

The New Zealand dollar is stronger by 1.7% at 1.4348 a dollar after the Reserve Bank of New Zealand said further rate cuts might be necessary. The bank held rates at 2.25%, as expected.

The euro is stronger by 0.3% at 1.1359 after the number of people out of work in Germany fell by a seasonally adjusted 16,000. This was the seventh consecutive drop, and much greater than the expected 4,000 increase. The jobless rate remained at 6.2%, which Bloomberg notes is the lowest level since German reunification.

The dollar index is weaker by 0.7% at 93.73 after Wednesday's Federal Reserve meeting when the policy-setting committee left its benchmark interest rate unchanged, as expected. Most economists now expect the next plausible chance of a rate hike is in June.

The British pound is stronger by 0.5% at 1.4613 after data showed that UK house-price growth slowed in April. The average price of a home gained 0.2% from the month prior, a slow-down from the previous month's 0.7%, according to Bloomberg. Moreover, the annual rate of growth slipped to 4.9%, down from 5.7%.